The present invention relates to passive infrared motion detectors of the type used in residential outdoor lighting fixtures, for example, to illuminate a walkway or driveway when a person or automobile approaches. The invention is more particularly directed to an arrangement for making the motion detector an inconspicuous element of the lighting fixture and to an arrangement for adjusting the motion detector range.
Early passive infra-red motion detectors used for activating outdoor lighting fixtures were big and bulky. They were only used with floodlights or with other non-decorative, primarily utilitarian lighting. The motion detectors of that time were contained in a separate, bulky and conspicuous housing that was unsuitable for use with stylish decorative lanterns commonly mounted in a prominent position by the front door of a house to welcome visitors. Later, an inexpensive flexible plastic lens was developed—the so-called flexible segmented Fresnel lens—that enabled more compact and less conspicuous motion detectors to be designed. Once the motion detectors had evolved to be smaller and less obtrusive, they started to be used with decorative lighting fixtures as well.
Decorative lighting fixtures have a rich heritage apart from motion detectors that stems from centuries of technical advancement and artistic creativity. There are many styles available to consumers today that have their origins in earlier lanterns designed for non-electric lighting. The earliest lanterns had an open bowl that held a lamp fuel such as animal fat or grease, tallow or oil and a wick extending out of the bowl. This lamp, used for centuries, evolved from a primitive utilitarian lamp to a highly refined decorative lantern as craftsmen made changes to incorporate functional and stylistic advances. For example, over the centuries the wick arrangement was configured so that excess oil or fat would drain back into the bowl instead of dripping onto the ground; the open bowl was reconfigured with a hinged cover with wick outlet; multiple wicks were added; arrangements were devised for carrying and hanging the lantern; and the lantern was crafted from such materials as iron, copper, bronze, pewter and silver, each material permitting its own decorative styling. Over time new fuels were introduced, each with its own characteristic technical requirements that stimulated changes in lantern design to meet the needs of the new fuel. New designs evolved for such fuels as whale oil, the so-called burning fluids (alcohol, alcohol and turpentine blends, camphene), coal oil, kerosene, and gas. Notable inventions influenced lantern designs as well—the Argand burner for whale oil, the von Welsbach mantle for gas, and of course the incandescent electric light. Perhaps more than by technical advancement, lantern styles have been influenced by the aesthetic creativity of artisans over the centuries, who developed imaginative designs complementing the fashionable architectural styles of the period. The result is that the consumer today is confronted with a profuse selection of lanterns—lighting purveyors typically offer them in categories of style such as Colonial, Victorian, Art Nouveau, Arts and Crafts, Mission, English Tudor, Queen Anne, Georgian Revival, Spanish, Mediterranean, and Contemporary, to mention only a few—conveying impressions of old world charm, geographic association, or architectural period and incorporating stylistic lines from centuries of development. Only a relatively few of the available lantern styles lend themselves to building in an inconspicuous motion detector.
When motion detectors were first used with outdoor decorative lanterns, they were located in a small housing mounted on the lantern backplate. The backplate is an intermediate plate to which the lantern is attached and which in turn is mounted on a wall over an electrical junction box. Such a backplate-mounted motion detector is illustrated in FIG. 1 of U.S. Pat. No. 5,590,953 of Haslam et al. This arrangement became commercially feasible because of the segmented Fresnel lens, which permitted the motion detector housing to be sufficiently compact that it diminished the distraction from the decorative nature of the lighting fixture. With a backplate-mounted motion detector a large number of lantern styles could be motion-activated. The presence of the motion detector was nevertheless plainly evident, and some lantern styles could not be used with the backplate-mounted motion detector because a portion of the lantern necessarily extended in front of the motion detector and blocked the motion-detecting action.
In recent years the trend has been to integrate the motion detector into the decorative lantern itself and thus remove it from the backplate. Early integrated decorative fixtures simply added a decoratively shaped element to house the motion detector. This often took the form of a cylinder of expanded diameter and may be seen for example in FIG. 2 of U.S. Pat. No. 5,590,953 of Haslam et al. While this form of design provided a decorative lantern with integrated motion detector, it could not be incorporated into most of the classic and contemporary lantern styles without interfering with the original style, if it could be incorporated at all.
A first undertaking to incorporate the motion detector into a classic lantern style is disclosed in U.S. Pat. Nos. 5,282,118 and 5,434,764 of Lee et al. In these patents the motion detector is hidden in a generally spherical, but somewhat flattened housing, which is of a general form that has been found in lantern styles for several centuries and which originally served as an oil reservoir in oil-burning lamps. This integrated motion detector preserved the classic lantern style without noticeably compromising the outward appearance.
Despite these developments there still exist a plethora of historic and contemporary decorative lantern styles that are not amenable to a hidden motion detector in the fixture body. Problems arise when the motion detector is incorporated into the body of the lantern because there is limited space for the optical and electronic elements and because the interior volume available for the motion detector elements may be awkwardly shaped. The volume of the space to work with and the shape of the decorative exterior fixture walls impose constraints on the technical design of the motion detector. To add a motion detector to many stylistic lantern designs, it has been necessary either to add a further housing element to the lantern, adversely altering the lantern style, or to place the motion detector on the backplate. To date, many such historical and contemporary styles have had to go without integrated motion detectors.